What operating system do you put on a legacy Pentium one computer. Let's see Mac os/x will not work. None of the latest Microsoft offerings of 8, 9, or 10 will work. Most linux major linux versions need at least a Pentium II. Enter Slackware 14. You can install it on a Pentium I thereby keeping lots of older computers viable a while longer. They would be good starter computers as a stop gap to keep a IT budget in line. One thing that should mentioned is Slackware can go on a variety of systems including the Raspberry Pi and is definitely not limited to older systems.
Traditionally to install an operating system, you need a cd/dvdrom or a boatload of floppy disks and a hard disk for the operating system to be installed on for each system. We used a compact flash with an ide to compact flash adaptor for the hard drive. We also wanted to avoid all the making of media, though we did need to make a minimal floppy disk to get the install started. On floppy could be used for multiple machines in a layered install process. What floppy disk do we need? We need first to make a pre-execution environment boot disk . Pxeboot disk for short. The we just need a simple web server to make a couple of files available on the network. To make the floppy disk, you will need to go to romomatic.net
You will want to customize the image by putting in the details for the server that will hold the special files. That means you need to download initrd.img and bzImage from ftp://ftp.slackware.com/pub/slackware.slackware-14.1 and copy them to the slack directory on the server. The ip address should be the actual ipaddress of your web server that is going to host the files.
chain http://192.168.3.88/slack/bzImage load_ramdisk=1 prompt_ramdisk=0 rw printk.time=0 nomodeset SLACK_KERNEL=huge.s
Then you need to start the install. (More information at: http://docs.slackware.com/slackware:install)
For the source you will want to use install from ftp/http server usually option 4. That saves having to make a lot of install cd's.
If you have you have used linux before the rest should be pretty straight forward. For our installation, when the software started downloading, I hit the sack and planned to finish the install when I woke up. The system was waiting there for me to add the last finishing touches to the install and fairly quickly we were up and running linux on a Pentium 1 without any per se Microsoft products!. Also see http://docs.slackware.com/slackware:install for some post install suggestions. Have fun!
Update: We turned the machine into a web server with httpd, php, and mariadb. First web app installed was the Flatpress blogging software.